rennerfelt



l. RENNERFELT.

ELECTRIC FURNACE.

APPLICATION FILED MAY I2. 1919.

1,3 13,834, Patented Aug. 19,1919.

Mr /rsss as: .Znrgn' vof rvAn RENNERFELT, or DJUBSHOLM; SWEDEN,

ELECTRIC FURNACE.-

Specification of Letters Patent. Patented Aug. 19, 1919 Application filed May 12, 1919. Serial No. 29Q,591.

glass, enamels and other materials in cru= cibles or melting pots.

To obtain this object I propose to arrange vertical or nearly vertical electrodes in a plane in the center of a furnace room, the electrodes being practically parallel to each other. Arcs burning between the lower ends of the electrodes and an elongated conducting bed underneath, projecting from the bottom of the furnace room, generate an intense heating zone, emitting heat to both sides. Crucibles or glass melting pots to be heated are placed on one or preferably both sides of and along the heating zone-- The rays of heat strike the crucibles not only directly but also indirectly by reverberating downward from the roof, if a proper curvature is given to this. The central conducting bed underneath the electrodes should preferably be made of a block of carbon or graphite supported on a pro jection of carborundum or other very refractory material. To protect the contact block from being oxidized or volatilized it may be covered with a quantity ofpreferably pulverized graphite or carbon. The presence of the powder als promotes smooth burnin ofthe arcs by igtroducing a considerab e resistance in se 'es with the arc. The number of electrodes depends princi-,' pally on the nature of the current, but also on the size of the-furnace. When utilizing.

three phase current the number of elec trodes should preferably be three, but if the furnace room is rather long, the number of electrodes may be a multiple of three.

In the case of two phase current'the number of electrodes is two or a multiple of two. If the furnace is run with single phase or direct current, the power may be divided on two or more electrodes.

To facilitate introduction or removal of the crucibles openings are to be provided at one or both ends of the furnace room. If

the length of this is rather great, openings may be provided also in the other sides of the furnace room, one for each crucible.

If ,glass is to be 'melted for blowing purposes, openings are provided in the side walls slightly above the crucibles for the introduction of the glass blowers pipe.

The shape of the crucible may be rectangular, oval or round or of any form preferred. Special openings, one at each end of the furnace room, permit replacement of the carbon block contact, when this is required for any certain reason. Such parts of the walls, which are especially exposed to an excessive heating from the arcs,.are to be protected by blocks of carborundum, zirconla or other suitable material.

' According to a modification of the invention the electrodes, if considerably more than three are used, may be arranged, not.

in a plane, but in a curved surface, for instance on a cylinder. The crucibles are in such a case to be arranged on the outside of the cylinder of the electrodes, between this and the cylindrical wall of the furnace. To provide contacts for the arcs a centrally located projection from the bottom is covered with carbon in any preferred form. To facilitate removing of the cruciblesfrom the furnace openings corresponding to each crucible must be provided in the cylindrical wall of the furnace; Other openings slightly above aforesaid openings permit the introduction of glass blowers pipes or other tools if necessary.

A furnace built according to the present invention is illustrated on the accompanying drawing, in which Figure 1 is a vertical section taken at lines y-y in Fig 2, which is a horizontal section taken at lines aP-w in Fig. 1. A modified form of a furnace is illustrated by Fig. 3, which is a horizontal section of a circular furnace. Similar letters refer to similar parts in the several views.

Vertical or nearly vertical electrodes 1 are projected from above through a roof 2 into a furnace room. A projection 3 from the Fig. 2 or in a circle as in Fig. 3. In the former case a plane heating Zone is generated, in the latter case a circular or, rather, cylindrical heating zone. Rays of heat8 emanate from the heating zone toward cruci-' bles or melting pots 9 located between the heating zone and the surrounding furnace wall.

The contact block 3 'may be replaced through a door 12 through which the con-- tact powder may also be replaced. By properly shaping the curve of the inside of the roof the heat-rays from the arcs, which are going upward, may be made to reflect downward into the crucibles as in ordinary.

reverberatory fuel heated furnaces. The

furnace in Fig. 2 has only twocrucibles on each side of the electrodes but the number .of crucibles may be greatly increased by increasing the length of the furnace and the number of the electrodes correspondingly. Having now fully described my invention, I claim:

1. In an electric furnace the combination of a plurality of electrodes suspended from above into a furnace room in a substantially vertical plane, a projection from the bottom of the furnace room underneath the electrodes, a conducting layer of carbon in suitable form on the said projection forming contacts for arcs from the electrodes and crucibles on the bottom of the furnace, along the heating zone of the arcs.

2. In an electric furnace the combination of a plurality of electrodes suspended from above into a furnace room in a substantially cylindrical surface, a projection from the bottom of the furnace room underneath the electrodes, a conducting layer of carbon in suitable form on the said projection forming contacts for arcs from the electrodes, crucibles in the space surrounding the cylindrical heating zone and openings in the furnace wall corresponding to each crucible.

Signed at Stockholmin the county of Stockholms Lan and State of Sweden this 15th day of April, A. D. 1919.

IVAR RENNERFELT.

Witnesses GRETA PRIEN, ELIU WAHMAN. 

